In a typical printer, media trays store media sheets within the printer. During the printing cycle, a media transport system retrieves media sheets from a tray, routes the media through the printer to receive an image, and then ejects the media into an output tray for collection by a user. In some printers, separate media handling components or printer subassemblies perform the functions described above. For example, the printer could include a subassembly that retrieves a single media sheet from a stack of media and then transfers the sheet to another subassembly that conveys the sheet to a print head or image drum where the media sheet receives an image. In order to deliver an acceptable product to the user, each subassembly should transfer media sheets to the next subassembly without jamming or damaging the sheet.
Manufacturers refer to the junction between two printer subassemblies as a media path transition. Media path transitions include guides or baffles that position the media sheet for proper reception by the next subassembly. Typically, the guides include a surface that transfers the media sheet without jamming the edges or bending the corners. The characteristics of the guide depend on the functionality of the printer component or subassembly upon which the guide operates. For example, some subassemblies transport media in two directions, while other subassemblies rotate the media sheet. Still other subassemblies include access doors that open to allow a user to inspect the condition of the media path. Therefore, different subassemblies require different types of guides to direct media across the media path transition.
When guiding media subject to bidirectional movement, manufacturers commonly utilize wide baffle openings or “funnels,” preceded by a control point. Each funnel includes two opposing surfaces that form a gradually constricting media path, thereby directing the media sheet into the control point. The control point includes an idler and drive roller pair. The idler roller rests upon the drive roller to form a nip. As the funnel directs media into the nip, the roller pair accurately directs the media sheet across the media path transition to the next printer component or subassembly. For an even greater level of accuracy, the receiving subassembly may include a second roller pair preceded by a second funnel to accept the media sheet. Wide baffle openings and control points effectively direct bidirectional media between printer subassemblies; however, printers commonly use other types of guides as well.
Another type of guide utilizes interdigitated or interlaced “fingers” to transition the media between printer subassemblies. In a typical arrangement, the output of a subassembly includes a first member that spans the width of the media path. The member includes a plurality of fingers or curved protrusions that extend away from the media path. Adjacent fingers of the first member are separated by a distance that enables the fingers on a second member to be received between the adjacent fingers of the first member. Similarly, the fingers of the first member fill spaces between adjacent fingers in the second member. Thus, the interdigitated fingers form a continuous and overlapping surface, for directing media sheets along a path. Generally, such interdigitated finger media guides work well; however, some types of interdigitated finger arrangements may present structure to rotating media that may catch corners or edges of certain types of media.